Elastomeric pump

ABSTRACT

An elastomeric pump comprises a rigid base member and an elastomeric upper member having a dome-shaped part and an elongated lip or flat member extending from a region of the periphery thereof and spaced a small distance above the base. An inlet pipe enters through the base member under the dome and is normally covered by a flat valve. An outlet opening enters under the flat member and is surrounded by an annulus extending into contact with the flat part of the upper member. Pumping is effected by repeated depression of the dome-like part of the upper member. In an alternative drip-free embodiment the elongated lip is secured to the base about its periphery except for its tip which is pre-stressed to abut the base. When the dome is depressed liquid in the pump forces the tip of the lip upward to provide an egress for the liquid along the upper surface of the base.

United States Patent [191 Cocita June 28, 1974 ELASTOMERIC PUMP PrimaryExaminer-Stanley H. Tollberg [76] Inventor: Arliene N. Cocita, 11506Newport Atmmey Mill Rd., Wheaton, Md. 20902 22 Filed: Apr. 12, 1973 [57]1 pp o 350 622 An elastomeric pump comprises a rigid base member RelatedUS. Application Data Humphrey 222/207 and an elastomeric upper memberhaving a dome shaped part and an elongated lip or flat member extendingfrom a region of the periphery thereof and spaced a small distance abovethe base. An inlet pipe enters through the base member under the domeand is normally covered by a flat valve. An outlet opening enters underthe flat member and is surrounded by an annulus extending into contactwith the flat part of the upper member. Pumping is effected by repeateddepression of the dome-like part of the upper member. In an alternativedrip-free embodiment the elongated lip is secured to the base about itsperiphery except for its tip which is pre-stressedto abut the base. Whenthe dome is depressed liquid in the pump forces the tip of the lipupward to provide an egress for the liquid along the upper surface ofthe base.

12 Claims, 8 Drawing Figures mum m4 SHEET 1 (If 2 ELASTOMERIC PUMP CROSSREFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of my U.S. Pat. application Ser. No. 246,176, filedApr. 21. 1972, and entitled Elastomeric Pump now abandoned.

BACKGROUND OF THE INVENTION The present invention relates generally tofluid pumps and more particularly to fluid pumps of the type which aremounted on the top of bottles from which liquids are to be dispensed bya user.

There is disclosed in US. Pat. No. 3,486,663, a fluid pump or checkvalve which consists of an elastomeric member adapted to fit forinstance on the end of a bottle for the purpose of pumping fluid fromthe bottle. A series of chambers are defined by the pump which chambersare isolated from one another by flexible barriers constituting one wayvalves. When the elastomeric member is depressed repeatedly by a userfluid is caused to flow from chamber to chamber and eventually outthrough an exit port. As stated in the aforesaid patent, many advantagesarise from the use of this general approach to pumping liquids and morespecifically the device is considerably simpler and therefore lessexpensive than the prior art mechanical pumps and less subject tocorrosion, etc.

Although the device of the aforesaid US. Pat. is a great improvementover the prior art mechanical pumps, the configurations employed are farfrom optimum and require different devices for a simple check valve onthe one hand and a pump and check valve combination on the other. Thedevice of the prior patent in its simplest form, that is, the checkvalve, requires a two chamber device in which the input channel opensinto one chamber and the output channel opens into the other chamber.The two chambers are separated by an elongated flexible memberwhich'must be able to maintain a long line contact with the rigidplastic base to provide proper operation. When the apparatus is intendedto be employed as a pump a three chamber device is required with thethree chambers arranged in seratum and the inlet pipe entering into thechamber at one end of the series and the outlet pipe entering into thechamber at the other end of the series. Two flexible members define thepartitions between the three chambers and are required again to maintainisolation between the chambers over an elongated line surface. As aresult of the above arrangement, the prior art devices set forth in thepatent mentioned above are relatively complex requiring considerablymore of the plastic material than might otherwise be necessary andrequiring relatively expensive molds for formation of the devices fromthe raw plastic material. Further the inlet and outlet pipes are alwaysin communication with their respective chambers and contaminationparticu larly through the outlet pipe may be a problem.

It is an object of the present invention to provide an elastomeric pumpand/or check valve in which a single device serves both purposes and inwhich elongated line contacts between multiple chamber dividers areeliminated and wherein there is only one chamber.

SUMMARY OF THE INVENTION The pump and check valve of the presentinvention comprise a single chamber device comprising a rigid basemember and an upper member comprising a flexible hollow generallysemispherical (dome-like) plastic member having an elongated flatflexible part extending therefrom over about a angle thereof. Thedome-like part of the upper member is sealed about approximately 270 ofits periphery directly to the rigid base. The elongated flat flexiblemember extends outwardly from the 90 unsecured region over but spacedfrom a similarly shaped part of the base and contacting a raised annulusdisposed about the outlet pipe and extending upwardly from the floor ofthe otherwise flat rigid base member. The interior wall of the dome-likemember has a tongue or flap formed integrally therewith and extendingdownwardly and over an inlet orifice from the inlet pipe. Smallprotuberances may extend downwardly from the flap to hold it off thebase and permit unimpeded flow through this region.

When pressure is applied to the top of the elastic dome and it iscollapsed, the interior of the dome, the chamber, is pressurized and thefliap is forced securely against the rigid base member to seal theopening into the chamber. Concurrently the pressure in the chamberforces the elongated flat flexible part of the upper member upwardlyagainst ambient air pressure and i permits air or other fluid in the:chamber to escape through the outlet tube. When the dome is released,its natural resilience returns to its normal position, fluid is suckedthrough the inlet tube into the partial vacuum created thereby and thepartial vacuum now existing under the flat elongated part of the uppermember causes the plastic to be forced downwardly against the annulusformed around the outlet tube thereby sealing the outlet tube,preventing air from entering the chamber. When the plastic or flexibledome end is again depressed, the fluid that was sucked up into thechamber during the prior expansion cycle is expelled through the outlettube.

It is thus seen that a single chamber member may be employed to providethe pumping action that multiple chamber extended line contact flapvalve arrangements now provide and that the internal structure of thedevice is such as to reduce mold and material costs. Also the inlet andoutlet tubes are always covered when the device is not in use andproblems with contamination are reduced.

In a drip-free alternative embodiment the pump includes the dome and lipbut eliminates the outlet pipe extending through the base member and theraised annulus surrounding that outlet pipe. Instead the lip edge issecured to the base except at its tip which is prestressed to normallyabut the base in sealing relation. When the dome is collapsed, liquid inthe pump forces the tip of the lip away from the base and flows out ofthe pump along the base surface. lUpon release of pressure from thedome, the tip of the lip returns to the base, sealing the pump againstliquid egress.

It is therefore an object of the present invention to provide anelastomeric pump which comprises a single chamber member of relativelysimple configuration and in which such a member may serve both as a pumpand a one way check valve in its simplest form.

It is another object of the present invention to provide an elastomericpump in which the interior of the device is isolated from the inlet andoutlet pipe during periods of non-use.

It is another object of the present invention to provide a singlechamber device having two inlet passages; one of which is sealed and theother of which is opened when pressure is produced in the chamber and inwhich the above condition is reversed when a partial vacuum is createdin the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The above and still further objects,features and advantages of the present invention will become apparentupon consideration of the following detailed description of one specificembodiment thereof, especially when taken in conjunction with theaccompanying drawings, wherein: FIG. 1 is a three dimensional view inperspective of one embodiment of the present invention fitted to the topof a bottle;

FIG. 2 is a sectional view of the pump of the present invention securedto the top of a bottle or similar container taken along line 2--2 ofFIG. 1;

FIG. 3 is a sectional view along line 33 of FIG. 2;

FIG. 4 is a longitudinal sectional view similar to FIG. 2 showing theapparatus of the present invention with the dome substantially fullydepressed and rising or expanding back to its normal position;

FIG. 5 is a view similar to FIG. 4 showing the operation of the devicewhen the dome of the flexible elastomer is being depressed;

FIG. 6 is a sectional view of an alternative embodiment of the presentinvention;

FIG. 7 is a top view in plan of the pump of FIG. 6; and

FIG. 8 is a sectional view similar to FIG. 6 showing the pump of FIG. 6with the dome substantially fully depressed.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically tothe figures of the accompanying drawings, the pump of the presentinvention comprises a base member 1 and an elastomeric upper member 2,the terms upper and lower referring to the position of these membersduring normal use of the device. The base member 1 is fabricated from arigid material preferably in this particular instance a rigid plasticand is adapted to be attached to a source of the fluid to be pumped. Inthe particular environment which has been selected for purposes ofillustrating the present invention, the fluid to be pumped is a liquidand it is contained in a bottle 3 having an externally threaded neck 4to which the base member is secured. Specifically in this particularsituation the base member has a hollow cylindrical wall 6 havinginternal threads 7 adapted to mate with external threads 8 formed on theneck 4 of the bottle. The hollow cylindrical wall 4 terminates in an endwall 9 having a centrally located passage 11 communicating internallywith a tube 12 adapted to extend to adjacent the bottom of the bottle 3for purposes of having the liquid pumped therethrough.

The base member 1 further comprises an elongated tapered part 13terminating in a downward drooping member 14 which is not at allessential to the invention but is employed for purposes of convenienceonly. The base member 1 has an upper wall 16 defined by recessing theupper surface of the member such as to define an upstanding wall or lip17 extending about the periphery of the upper surface 16 as defined bythe parts 9 and 13 of the base member 1. The drooping portion 14 of thebase member is not so recessed. A passage 18 extends through thedrooping member 14 of the base 1 and terminates in a vertical passage 19within the region 13 of the base member 1 and somewhat remote from thewall 9 of the base member. The passage 19 is surrounded in this area bya narrow raised annulus 21 which extends upwardly from the wall 16 at adistance from the wall 17 at all locations.

The upper member 2 comprises a hollow semispherical elastomericdome-like member 22 generally symmetrical with the axis of the hollowcylindrical mem bers of the base member 1. The hollow spherical ordome-shaped member 22 of the upper member 1 has extending therefrom alip-like or flat tapered part 23 which is positioned to overlie theregion 13 of the base member 1. The flat part 23 of the upper member 2has a downwardly depending peripheral wall 24 of such a height that alower surface, as viewed in FIG. 2, of the part 23 lies flat against thetop of the annulus 21 when the device is assembled.

. Assembly of the upper part 2 to the lower part 1 is by bonding byappropriate cements or other materials interiorly of the wall 17 at alllocations; the specific regions of bonding being illustrated by thethickened black wall regions 26 in the drawings. At the junction of thespherical part 22 and the flat part 23 there may be provided on thelower surface of the elastomeric member a series of small protrusions 27for causing the upper member to maintain specific spacing above thesurface 16 of the base member 1. These projections are spaced from oneanother so as not to interfere with the free flow of fluid through thedevice. In many instances the projections 27 may be eliminated.

To complete the structure of the upper member 2 there is provided a flap28 formed integrally with and extending downwardly from the innersurface of the dome-shaped member 22. The flap 28 overlies the passage11.

In the operation of the device, initially, the flap 28 is intended toseal the opening 11 whereas the flat part 23 of the upper member 22 isin contact with the upper surface of the hollow annulus 21 and seals thepassage 18. Thus the interior of the upper member 22 is isolated fromboth inlet and outlet openings when not in use. If now the dome-shapedmember 22 is depressed as illustrated in FIG. 4, the pressure thuscreated internally of the dome 22 forces the flap 28 securely againstthe surface 16 in the region of the orifice l1 and prevents air or otherfluid in the chamber from entering the passage 11, tube 12 and thus thebottle 3. Concurrently the increased pressure formed between the member2 and the base member 1 causes the flat part 23 of the upper member 2 tobe forced upwardly away from the annulus 21 thereby opening the passage19 to the pressurized fluid lying between the members 1 and 2. Thepressurized fluid is thus expelled through the passage 18-19.

Upon releasing the dome 22 as illustrated in FIG. 5 its naturalresiliency causes it to return to the position illustrated in FIGS. 1and 2 thus creating a low pressure in the region between the members 1and 2. The low pressure thus created causes fluid to rise in the tube 12and enter the interior of the dome region 22. The passage 18 at thispoint is sealed since the reduced pressure between the regions 13 and 23of the members 1 and 2, respectively, causes the member 23 to be forceddownwardly against the upper surface of the annulus 21. Thus it can beseen that the pressure created when the dome-shaped member is depressedseals the inlet pipe 11 and the reduced pressure created when thedome-shaped member 22 is released and returns to its normal positioncauses the outlet passage 18-19 to be sealed.

When the dome-shaped member 22 is again depressed the fluid previouslypumped into the interior of the member during the previous cycle ofoperation is expelled through the outlet passage 18-19 again by thecreation of the pressure interiorly of the domeshaped member 22 and thusthe pumping cycle is completed.

The annulus 21 may be eliminated if the flat part 23 of the upper membernormally contacts wall 16. In such an arrangement pumping pressures aregreater than in the illustrated embodiment.

Referring to FIGS. 6-8 of the accompanying drawings, there isillustrated an alternative, drip-free embodiment of the presentinvention. The rigid base member 31 includes an upper surface 32 onwhich the elastomeric member 33 is secured. The elastomeric memberincludes a dome 34 and a radially extending lip 36, similar to dome 22and lip 23 in FIG. 2. Likewise a flap 37, similar to flap 28, normallyoverlies inlet passage 38 which in turn communicates with the interiorof a bottle or the like from which liquid is to be pumped. At thejunction of lip 36 and dome 34 a series of small spaced protrustions 35project from the elastomeric member and are similar to protrusions 27 inFIG. 2. These protrusions continuously abut surface 32 to maintain thejunction between the lip and dome spaced by a specific distance fromsurface 32. In this manner, liquid is free to flow along surface 32 andaround protrusions 35 from the dome-covered portion to the lip-coveredportion. I

Surface 32 is contoured such that its apex or highest point 39 residesunder lip 36. From apex 39 toward the dome region the surface 32exhibits a gradual downward taper or slope; in the other direction(i.e., toward the outlet end of lip 36) surface 32 exhibits a somewhatmore severe downward slope.

Except for its forward. tip, the periphery of lip 36 is firmly secured,by adhesive or the like, to surface 32, as generally indicated at 40.The forward tip 41 of lip is not secured but is pre-stressed to normallyabut surface 32 in liquid-sealing relation. When the pressure inside thepump exceeds ambient pressure, however, tip 41 is forced upward and awayfrom surface 32 to permit liquid outflow from the pump.

With the exception of the outflow from the pump, operation issubstantially the same as described above for the pump of FIGS. 1-5.More particularly, liquid is introduced into the initially empty singlepump chamber by depressing dome 34 and then releasing. Upon release, thedome returns to its unflexed position due to its natural resiliency,thus creating a low pressure region in the pump chamber. The lowpressure causes fluid to rise in passage 38and enter the chamber. Upondepressing the dome again, as illustrated in FIG. 8, the liquid in thechamber is forced along surface 32, be-' neath lip 36, where it forcestip 41 away from the surface and flows out of the chamber. When theliquid in the chamber is depleted, or when the dome is released again,tip 41, by its own resiliency, returns to sealing relation with surface32 and prevents further liquid outflow from the pump chamber.

It is preferable that more than simply the periphery of tip 41 becontoured to normally abut surface 32. Specifically, and as bestillustrated in FIG. 6, a substantial length of the interior portion oflip 36 abuts surface 32 when the pressure in the chamber is less thanand equal to ambient pressure. This provides a seal of relatively longlength which improves the drip-free characteristic of the pump.Preferably this seal should begin proximate apex 39 and extends all theway to tip 41. This forces substantially all of the residual liquid inthe pump to flow down the gradual slope and back into the dome-coveredportion of the pump chamber, further assuring dripless steady statecondition of the pump.

The pump illustrated in FIGS. 6-8 has its base 31 contoured to provideparticular utility for dispensing hand cream or other liquid which isnormally dispensed directly onto the palm of the user. Specifically, theunder-surface of base 31 is contoured to include an arcuate portion 42adapted to receive the side of the forefinger of. theuser while thethumb is used to depress dome 24. In this position which is illustratedin FIG. 8, the palm of the users hand is positioned to catch liquidoutflow from beneath tip 41.

An important feature of the embodiment of FIGS. 6-8 resides in the factthat lip 36 is fixedly secured to surface 32 along the entirety of bothof its longitudinal sides but is merely resiliently biased againstsurface 32 at outlet tip 41 and along part of its interior regionupstream of outlet tip 41.

Another important feature of the embodiment of FIGS. 68 resides in thefact that liquid outflow proceeds along the upper surface 32 beneath tip41 and does not require that a specific outlet passage be defined in thebase member.

It1will be noted that in the structure of the present invention only asingle chambered device is provided and that the necessary valvingactions are effected by alternately blocking flow through the inlet andoutlet passages, respectively, and not by the expedient of isolatingthese passages from one. another through various intermediate chambersand valve walls.

It should be further noted that the member 22 does not have to bedome-shaped as such and that the member 23 does not have to beabsolutely flat, lie precisely parallel to the base member nor must itbe elongated to the extent illustrated in the accompanying figures ofthe present invention. The area of the surface of the member 23 issomewhat exagerated in these figures so that the operation of thisportion of the invention will be readily apparent to one skilled in theart, that is,

when a reduced pressure is created interiorly of the region between thenumbers 1 and 2, atmospheric pressure operating onthe outer surface ofthe member 23 causes the member 23 to seal the: passage 19.

The upper member is described as bonded to the base member and the basemember is described as rigid. Securing of the upper to the lower membermay be by mechanical means as well as bonding. Also the term rigid isused in the sense of a base member that does not materially deform underthe pressures normally in this type of pump. Further although the flap28 is illustrated as integral with the upper member, this is notessential to the invention and the flap may be secured to the basemember.

The materials which may be employed in the fabrication of the members ofthe present invention are well known in the art and for detailsreference is made to the aforesaid patent.

While I have described and illustrated one specific embodiment of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may beresorted to without departing from the true spirit and scope of theinvention as defined in the appended claims.

I claim:

1. An elastomeric pump comprising a base member having an upper surfaceand an integral resilient upper member overlying and secured generallyabout its periphery to said upper surface to define a fluid-tightchamber between the base and upper members, said upper member having anenlarged section and a lip-like section extending outwardly from an edgeof said enlarged section with the periphery of said lip-like sectionsecured to said upper surface, the interior portion of said lip-likesection being spaced from said upper surface, an inlet port enteringsaid chamber, a movable flap overlying said inlet port in said chamber,an exit port extending through said base member under the interiorportion of said lip-like section and means causing said lip-like sectionwhen in its unflexed position to seal said exit port.

2. The combination according to claim 1 wherein said movable flap isintegral with the interior surface of said upper section.

3. The combination according to claim 1 wherein said means is an annularprojection disposed about said outlet port and extending from said uppersurface of said base member into said chamber and into contact with aregion of said lip-like section in its unflexed position.

4. The combination according to claim 1 wherein said enlarged section isgenerally a semisphere.

5. The combination according to claim 1 wherein said lip-like sectionhasprojections extending from its interior portion toward said uppersurface of said base member to maintain said interior portion spacedfrom said upper surface.

6. A single-chambered elastomeric pump comprising:

a base member having an upper surface;

an integral elastomeric member secured to said upper surface of saidbase member in fluid-tight relation to define a single dome-shaped pumpchamber between said elastomeric member and said upper surface of saidbase member;

said upper surface of said base member having an inlet flow passagedefined therethrough and terminating in an inlet opening to said pumpchamber;

flap valve member disposed within said pump chamber and positioned toblock said inlet opening when the pressure in said pump chamber issubstantially equal to and greater than the pressure in said inletpassage, said flap valve member being adapted to unblock said inletopening when the pressure in said pump chamber is substantially belowthe pressure in said inlet passage; and

wherein said elastomeric member includes a flexible lip-like projectionextending radially outward from said dome-shaped chamber and overlyingsaid upper surface of said base member and defining an outflow regionbetween said projection and said upper surface, said dome-shaped chamberand said projection intersecting at a junction which is raised from saidupper surface such that said outflow region is in constant flowcommunication with said chamber, said projection being adhesivelysecured at least along its sides to said upper surface and arranged toblock flow communication between said outflow region and ambient whenthe pressure in said chamber is substantially equal to and less thanambient pressure, said projection being adapted to be flexed away fromsaid upper surface of said base member to expand said outflow region andunblock flow communication between said outflow region and ambient whenthe pressure in said pump chamber substantially exceeds ambientpressure.

7. The pump according to claim 6 wherein said liplike projectionincludes a tip at its end remote from said junction, said tip beingresiliently biased to abut said upper surface when the pressure in saidchamber is less than and substantially equal to ambient pressure, saidtip being otherwise unconstrained to permit flexure of i said tip awayfrom said upper surface when the pressure in said chamber substantiallyexceeds ambient pressure to thereby permit outflow of pump liquidbetween said tip and said upper surface.

8. The pump according to claim 7 wherein said upper surface is contouredto provide an apex located beneath said projection, said upper surfacebeing sloped downward from said apex toward both said tip and saidchamber.

9. The pump according to claim 8 wherein the interior portion of saidprojection is resiliently biased to abut said upper surface along asubstantial portion but not all of its length when the pressure in saidchamber is less than and substantially equal to ambient pressure.

10. A single-chambered elastomeric pump comprisa rigid base memberhaving an inlet passage defined therethrough and including an uppersurface at which said inlet passage terminates in an inlet opening;

an elastomeric member secured to said upper surface above said inletopening to define a single chamber between said elastomeric member andsaid upper surface, said elastomeric member comprising:

a dome portion;

a resilient flap valve member disposed within said dome portion andpositioned to flexibly block said inlet opening when the pressure insaid chamber is substantially equal to and greater than the pressure insaid inlet passage, said flap valve member being sufficiently resilientto unblock said inlet opening when the pressure in said pump chamber isbelow the pressure in said inlet passage;

an elongated projection extending substantially radially outward fromthe periphery of said dome portion along said upper surface;

said dome portion and said projection intersecting at a junction whichis maintained raised above said upper surface to permit liquid flowalong said upper surface from said dome portion to said projection;

said projection being fixedly secured to said upper surface along itsradially extending edges, and having a tip at its radially outermost endwhich is resilbeneath said projection, said upper surface being slopeddownward from said apex toward both said tip and said chamber.

12. The pump according to claim 10 wherein the interior portion of saidprojection is resiliently biased to abut said upper surface along asubstantial portion but not all of its length when the pressure in saidchamber is less than and substantially equal to ambient pressure.

1. An elastomeric pump comprising a base member having an upper surface and an integral resilient upper member overlying and secured generally about its periphery to said upper surface to define a fluid-tight chamber between the base and upper members, said upper member having an enlarged section and a lip-like section extending outwardly from an edge of said enlarged section with the periphery of said lip-like section secured to said upper surface, the interior portion of said lip-like section being spaced from said upper surface, an inlet port entering said chamber, a movable flap overlying said inlet port in said chamber, an exit port extending through said base member under the interior portion of said lip-like section and means causing said lip-like section when in its unflexed position to seal said exit port.
 2. The combination according to claim 1 wherein said movable flap is integral with the interior surface of said upper section.
 3. The combination according to claim 1 wherein said means is an annular projection disposed about said outlet port and extending from said upper surface of said base member into said chamber and into contact with a region of said lip-like section in its unflexed position.
 4. The combination according to claim 1 wherein said enlarged section is generally a semisphere.
 5. The combination according to claim 1 wherein said lip-like section has projections extending from its interior portion toward said upper surface of said base member to maintain said interior portion spaced from said upper surface.
 6. A single-chambered elastomeric pump comprising: a base member having an upper surface; an integral elastomeric member secured to said upper surface of said base member in fluid-tight relation to define a single dome-shaped pump chamber between said elastomeric member and said upper surface of said base member; said upper surface of said base member having an inlet flow passage defined therethrough and terminating in an inlet opening To said pump chamber; a flap valve member disposed within said pump chamber and positioned to block said inlet opening when the pressure in said pump chamber is substantially equal to and greater than the pressure in said inlet passage, said flap valve member being adapted to unblock said inlet opening when the pressure in said pump chamber is substantially below the pressure in said inlet passage; and wherein said elastomeric member includes a flexible lip-like projection extending radially outward from said dome-shaped chamber and overlying said upper surface of said base member and defining an outflow region between said projection and said upper surface, said dome-shaped chamber and said projection intersecting at a junction which is raised from said upper surface such that said outflow region is in constant flow communication with said chamber, said projection being adhesively secured at least along its sides to said upper surface and arranged to block flow communication between said outflow region and ambient when the pressure in said chamber is substantially equal to and less than ambient pressure, said projection being adapted to be flexed away from said upper surface of said base member to expand said outflow region and unblock flow communication between said outflow region and ambient when the pressure in said pump chamber substantially exceeds ambient pressure.
 7. The pump according to claim 6 wherein said lip-like projection includes a tip at its end remote from said junction, said tip being resiliently biased to abut said upper surface when the pressure in said chamber is less than and substantially equal to ambient pressure, said tip being otherwise unconstrained to permit flexure of said tip away from said upper surface when the pressure in said chamber substantially exceeds ambient pressure to thereby permit outflow of pump liquid between said tip and said upper surface.
 8. The pump according to claim 7 wherein said upper surface is contoured to provide an apex located beneath said projection, said upper surface being sloped downward from said apex toward both said tip and said chamber.
 9. The pump according to claim 8 wherein the interior portion of said projection is resiliently biased to abut said upper surface along a substantial portion but not all of its length when the pressure in said chamber is less than and substantially equal to ambient pressure.
 10. A single-chambered elastomeric pump comprising: a rigid base member having an inlet passage defined therethrough and including an upper surface at which said inlet passage terminates in an inlet opening; an elastomeric member secured to said upper surface above said inlet opening to define a single chamber between said elastomeric member and said upper surface, said elastomeric member comprising: a dome portion; a resilient flap valve member disposed within said dome portion and positioned to flexibly block said inlet opening when the pressure in said chamber is substantially equal to and greater than the pressure in said inlet passage, said flap valve member being sufficiently resilient to unblock said inlet opening when the pressure in said pump chamber is below the pressure in said inlet passage; an elongated projection extending substantially radially outward from the periphery of said dome portion along said upper surface; said dome portion and said projection intersecting at a junction which is maintained raised above said upper surface to permit liquid flow along said upper surface from said dome portion to said projection; said projection being fixedly secured to said upper surface along its radially extending edges, and having a tip at its radially outermost end which is resiliently biased to abut said upper surface in liquid sealing relation when the pressure in said chamber is substantially equal to and less than ambient pressure, said tip being sufficiently resilient to be flexed away from said upper surface when the pressure in said Chamber exceeds ambient pressure to thereby permit liquid to egress from said chamber along said upper surface and beneath said tip.
 11. The pump according to claim 10 wherein said upper surface is contoured to provide an apex located beneath said projection, said upper surface being sloped downward from said apex toward both said tip and said chamber.
 12. The pump according to claim 10 wherein the interior portion of said projection is resiliently biased to abut said upper surface along a substantial portion but not all of its length when the pressure in said chamber is less than and substantially equal to ambient pressure. 